Chrome tanning



Patented Aug. 31, 1937 UNITED STATES PATENT OFFICE Rhine, Germany,

dustrie Aktiengesellschatt,

Main, Germany No Drawing. Application January 3, No. 57,363. In GermanyJanuary 18 Claims.

The present invention relates to improvements in chrome tanning bytreating hides withtanning agents comprising chromium salts ofnontanning polybasic aromatic acids, as well as to the said tanningsemployed and the leather obtained therewith.

For chrome tanning by the single bath process, chromium salts ofinorganic acids or of aliphatic acids, such as formic acid or oxalicacid, have hitherto been used. The addition of fatty acid derivatives(Turkey red oils) during the tanning has also been proposed. In order toobtain leather having certain desired properties, the chrome tanning hasalso been carried out in conjunction with vegetable or synthetic tanningagents.

I have now found that very good and especially full leather can beobtained by treating hides with chromium salts of non-tanning poly- 20basic aromatic acids in the known manner, The

term polybasic aromatic acids, whenever used,

includes polybasic aromatic carboxylic and sulphonic acids. Suitableacids are for example phthalic acids, naphthalene-dicarboxylic acids,and naphthalene disulphonic acids and certain substitution productsthereof. The chromium salts of these acids may be obtained, depending onthe nature of the polybasic acid used, for example by the reaction oftheir alkali metal salts with neutral or basic chromium sulphate.

In many cases the procedure may also be that the hides are pretreatedwith one component and then treated with the other component, thetreatments being repeated if desired.

35 The tanning proceeds simply and rapidly.

When desired, as much as per cent of chromium oxide (calculated withreference to the finished leather) in combination with the correspondingamount of aromatic acid may be read- 40 ily incorporated with the hides.Thus for example by tanning in short baths an increase in weight andvolume of the leather of per cent and more can be obtained so that fullleather with the character of a combination tanning can be obtained in asimple manner. Pickling, neutralization at the conclusion of the tanningor deacidification of the hides, as for example before dyeing, may bedispensed with when the basicity of the bath is suitable, in particularwhen 50 employing chromium salts of weak aromatic acids.

In order to obtain leather having special properties the said chromiumsalts can also be employed together or in any desired sequence withother tanning agents. Thus hides which had assignor to I. G.

Farbenln- Franktort-on-the- 1930, Serial 19, 1935 Example 1 222 parts ofphthalic anhydride are dissolved in water with the addition of 120 partsof sodium hydroxide and the solution rendered neutral to litmus. From450 to 500 parts 01' chromium alum are then added to the solution. Intothe resulting solution (80 per cent of the weight of the unhaired hides)there are introduced delimed unhaired sheep hides, and the latter aretreated in the usual manner according to the single bath tanningprocess. In order to obtain ripe tanning, a little soda may be added tothe tanning liquor towards the end of the tanning if desired.

Emmple 2 148 parts of phthalic anhydride are dissolved in water with anaddition of 80 parts of sodium hydroxide and the solution is renderedneutral to litmus. A solution of basic chromium sulphate (Cr(OH)SO4)corresponding to 76 parts of CrzOs is then added.

Delimed non-pickled unhaired hides are treated with the resultingtanning liquor in a short bath (45 per cent of the weight or theunhaired hides). 4

A ripe-tanned leather is obtained without any neutralization of thetanning liquor with soda being necessary.

Example 3 Delimed and bated unhaired calf hides are fully tanned in ashort bath per cent of the weight of the unhaired hides) with a solutionof 276 parts or i-nitronaphthalene-3.8-disulphonic acid sodium salt anda solution'of basic chromium sulphate (Cr(OI-I)SO4) corresponding to 76parts of CrzOa.

Example! 1200 parts 01' shaved non-deacidifled chrome leather, which hadbeen prepared according to the chrome-singleor -two-bath-process in theusual manner are treated with the tanning liquor described in Example 2horsed up overnight,

5 washed, dyed by any of the standard methods, fat-liquored and finishedas usual. In order to obtain leather of an especially high fullness atreatment with synthetic tanning agents, as for example withcondensation products of naphthalene sulphonic acid and formaldehyde canbe inserted at any desired stage of the tanning process. Instead of thetan prepared from phthalic acid anhydride described above there can alsobe employed the corresponding amount of a similar \5 tan but preparedfrom tetrachlor phthalic acid.

Example 5 1000 parts of dry East-Indian sheep leather are thoroughlywetted with warm water, if desired with an addition of 5 parts ofcalcined sodium carbonate and treated in the same manner as described inExample 4.

Example 6 1000 parts of alum ripe leather are wetted and after-tanned inthe manner described in Examples 4 and 5.

What I claim is:

1. The process of tanning which comprises treating hides with a chromiumsalt of a nontanning polybasic aromatic carboxylic acid.

2. The process of tanning which comprises treating hides with a chromiumsalt of a nontanning polybasic aromatic carboxylic acid and with afurther tanning agent.

3. The process of tanning which comprises treating hides pretanned bymeans of known tanning agents with a chromium salt of a nontanningpolybasic aromatic carboxylic acid.

4. The process of tanning which comprises first treating hides with achromium salt of a nontanning polybasic aromatic carboxylic acid andthen treating them with a known tanning agent.

5. The process of tanning which comprises treating hides with a chromiumsalt of a nontanning po-lybasiccarboxylic acid of the benzene series.

6. The process of tanning which comprises treating hides with a chromiumsalt of phthalic acid.

7. The process of tanning which comprises treating hides with a chromiumsalt of tetrachlor phthalic acid.

8. The process of tanning which comprises first treating hides with atanning chromium salt and then with a non-tanning polybasic aromaticcarboxylic acid compound.

9. The process of tanning which comprises first treating hides with atanning chromium salt and then with a non-tanning polybasic aromaticcarboxylic acid salt.

10. The process of tanning which comprises repeatedly first treatinghides with a tanning chromium salt and then with a non-tanning polybasicaromatic carboxylic acid compound.

11. Leather containing a chromium salt of a non-tanning polybasicaromatic carboxylic acid.

12. Leather containing a chromium salt of a non-tanning polybasiccarboxylic acid of the benzene series.

13. Leather containing a chromium salt of phthalic acid.

14. Leather containing a chromium salt oi! tetrachlor phthalic acid.

15. Chrome-tanning agents comprising a chromium salt of a non-esterifiednon-tanning polybasic aromatic carboxylic acid.

16. Chrome-tanning agents comprising a chromium salt of a non-esterifiednon-tanning polybasic carboxylic acid of the benzene series.

17. Chrome-tanning agents comprising a chromium salt of non-esterifiedphthalic acid.

18. Chrometanning agents comprising a chr0- mium salt of non-esterifiedtetrachloro phthalic acid.

EUGEN IMMENDOERFER.

